The present invention relates to methods and apparatus for over-coating closed cell elastomeric foam material without engendering reactions which may cause blistering or bubbling at the surface of the foam during coating. The invention is especially suitable for use in making foam weather seals.
Weather seals have been made of closed-cell plastic foam material which are over-coated to form a skin having a lower coefficient of friction than the foam material, see, for example, the following patents: Waskewicz, U.S. Pat. No. 4,238,260, issued Dec. 9, 1982; Yackiw, U.S. Pat. No. 4,328,273, issued May 4, 1982; Yardley, U.S. Pat. No. 4,537,825, issued Aug. 27, 1985; Yackiw, U.S. Pat. No. 4,535,564, issued Aug. 29, 1985; Collinder, U.S. Pat. No. 4,538,380, issued Sep. 3, 1985; Yackiw, U.S. Pat. No. 4,656,785, issued Apr. 14, 1987; and Mertinooke, U.S. Pat. No. 5,192,586, issued Mar. 9, 1993.
It has been found that when the coating is over preformed plastic or thermoset elastomer foam material such as closed-cell EPDM rubber, reactions occur during extrusion which give rise to bubbles and poor adhesion of the coating. Such rubbers have been developed in the past, see, for example, Brenner, U.S. Pat. No. 4,181,780, issued Jan. 1, 1980, however, neither the problem caused by the extrusion of the molten plastic for over-coating has not been either addressed or solved.
Accordingly, it is the principal object of the invention to provide improved methods and apparatus for making weather seals utilizing flexible strips (preferably cylinders or tubes) of closed-cell foam material such as thermosetting EPDM.
It is a further object of the present invention to provide improved methods and apparatus for over-coating a skin of plastic material by extrusion thereof on a closed-cell foam substrate, which is operative to raise the temperature of the substrate above a temperature critical to induce off-gassing of any materials or moisture in the pores thereby substantially eliminating the release of gas from the pores during over-coating, which can affect the quality of the coating.
It is still a further object of the present invention to provide an improved method of over-coating closed-cell foam materials which enables such materials to be prefabricated and unwound from reels into an extruder which carries out the over-coating process.
It is still a further object of the present invention to provide improved methods and apparatus for over-coating foam material in the production of weather-stripping or other products using the foam material by pre-curing, pre-heating or out-gassing a surface layer of the foam while the foam is fed through an oven chamber through which heated air is blown.
Briefly described, a weather seal made in accordance with the invention has a flexible foam substrate which prior to the extrusion of a skin of molten plastic material is heated to outgas at least a surface layer thereof. This layer is a crust which is essentially devoid of cells from which gas can be released. Accordingly, during extrusion and over-coating, the foam substrate is essentially unreactive with the skin material and the quality of the skin as regards to its adhesion to the substrate and smoothness is improved.